This continuation of the NlDA Center at UCLA will further characterize key molecules and mechanisms involved in opioid receptor regulation with the broad goal of more clearly understanding the processes of tolerance, dependence and withdrawal associated with drugs of abuse. This basic research ultimately will permit the development of human probes and reagents for clinical investigations addressing differential diagnosis and treatment. The focus of the continuing research of the Center is based primarily upon our successful isolation of a delta opioid receptor gene (DOR-1) and draws upon the breadth of opioid pharmacological and neurochemical accomplishments of the Center. The program comprises five major research areas: 1) The characterization of gene(s) and mRNAs encoding DOR-1. 2) The determination of the structural basis for opiate alkaloid and opioid peptide recognition and for signal transduction. 3) The identification and structural characterization of opioid receptors related to, but distinct from, DOR-1. 4) The analysis of opioid receptor neuroanatomical localization and relationship with other neurotransmitter systems implicated in drug abuse. 5) The understanding of mRNA regulation, post-translational modifications and intracellular trafficking of opioid receptors in both normal and drug perturbed states. The resources and expertise incorporated in the Center span techniques of molecular biology (cDNA cloning, mRNA analysis, genomic analysis, mutagenesis and expression), protein and peptide chemistry (peptide synthesis, peptide and protein purification, protein sequencing), analytical neurochemistry (mass spectroscopy, immunoassay, amino acid analysis), neuropharmacology (receptor binding, second messenger systems, microdialysis, behavior), and histochemistry (immunocytochemistry and in situ hybridization). Functionally the Center's research areas are highly integrated, interactive and interdependent. The continued application of this successful multidisciplinary and collaborative approach will lead to a more precise understanding of the molecular mechanisms underlying the addictive process and thus provide a basis for improved clinical methods for ameliorating the problems associated with drugs of abuse.